Lead author Jonathan B. Brown, an investigator with the Kaiser Permanente Center for Health Research in Portland, Ore., said Metformin is recommended as a first-line agent in the treatment of type 2 diabetes, but in most patients it eventually stops working, forcing them to take additional medications to control their blood sugar.
"This is an important finding for the 30 million people world-wide who are diagnosed with type 2 diabetes every year," Brown said in a statement.
"The sooner they start taking Metformin, the better and longer it seems to work."
Researchers used electronic health records to track nearly 1,800 people with diabetes in Kaiser Permanente's health plan in Washington and Oregon for up to five years.
The study, published in Diabetes Care, found Metformin failed at a rate of 12 percent a year for the patients who began taking it within three months of diagnosis, but failed 21.4 percent per year for patients who started taking it 1-2 years after diagnosis.